Turbine flow regulating valve system

ABSTRACT

A regulated two-stage turbocharger system is described. The turbocharger system includes high-pressure and low-pressure turbocharger units in communication with one another. The turbocharger system includes a valve system having valve members that are independently controllable so as to selectively control the gas flow into the turbine portions of the high-pressure turbocharger and the low-pressure turbocharger units. The valve members are asymmetric, e.g., they possess differing areas (e.g., perimeters, diameters and/or the like) with respect to one another.

CROSS-REFERENCE TO RELATED APPLICATION

The instant application claims priority to U.S. Provisional Patent Application Ser. No. 60/635,769, filed Dec. 14, 2004, the entire specification of which is expressly incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to turbochargers for use in automotive applications, and more specifically to control systems for use in regulated two-stage and sequential turbochargers.

BACKGROUND OF THE INVENTION

Turbochargers are generally well known in the art. Basically, a turbocharger is a centrifugal air pump that is driven by the engine's exhaust gas. The turbocharger forces an additional amount of air or air-fuel mixture into the engine, which aids in the increase of combustion pressure and engine power. This allows a relatively smaller engine to deliver acceptable fuel economy during normal driving conditions, and to have the increased power characteristics of a larger engine when needed. Turbochargers have been incorporated into both gasoline and diesel engines, for both commercial and passenger vehicle applications.

Examples of turbocharger technology can be found with reference to commonly assigned U.S. Pat. Nos. 6,089,019 to Roby; 6,263,672 to Roby et al.; 6,415,846 to O'Hara; 6,543,228 to Deacon; 6,694,736 to Pfluger; 6,709,160 to Ward et al.; 6,715,288 to Engels et al.; 6,802,184 to Huter et al.; and U.S. Patent Application Publication Nos. 2003/0206798 to Allmang et al.; 2004/0037716 to Jaisle; 2004/0062645 to Decker et al.; 2004/0088976 to Jaisle; 2004/0134193 to Klingel; 2004/0194447 to Roby; and 2004/0197212 to Roby, the entire specifications of all of which are expressly incorporated herein by reference.

A recent development in turbocharger technology has been regulated two-stage or sequential turbochargers, in which two relatively smaller turbocharger units are used instead of a single relatively large conventional turbocharger. These regulated two-stage turbocharger systems typically employ a relatively smaller, high-pressure turbocharger unit in series with a relatively larger, low-pressure turbocharger unit.

Unfortunately, conventional regulated two-stage turbochargers still exhibit unsatisfactory characteristics, especially during the overlapping transition period when the turbo speed of the smaller high-pressure turbocharger unit rapidly decreases and the turbo speed of the larger low-pressure turbocharger unit rapidly increases. This phenomenon is believed to be a momentary loss of torque that occurs before the low-pressure turbocharger unit has reached its particular requisite turbo speed. This “drop” in torque during the transition period is quite noticeable and is objectionable to many drivers, especially those driving expensive, high-performance luxury models.

Accordingly, there exists a need for new and improved regulated two-stage turbocharger systems that produce a relatively smooth and unnoticeable transition period between the operation of the high pressure and low pressure turbocharger units.

SUMMARY OF THE INVENTION

In accordance with the general teachings of the present invention, new and improved turbocharger systems are provided.

Specifically, the present invention provides a flow regulating valve for use between turbine stages in a series/sequential turbocharger system, with modulation of the stage loading that is believed to be critical to maintaining desired engine torque characteristics and transient response.

More specifically, the present invention employs two valve members. In accordance with one aspect of the present invention, the two valve members are of differing area and/or size (e.g., perimeter, diameter, port diameter, and/or the like) with respect to one another. In accordance with another aspect of the present invention, the two valve members (either being equally sized or of differing size and/or area) are operable to be opened (i.e., actuated) independently of one another.

By way of a non-limiting example, by using two valves of different port diameters, the smaller diameter port valve can be opened first, reducing the flow upon initial valve opening compared to two valves opening in parallel or two valves of equal port diameter opening at the same time. By way of a non-limiting example, when the first port flow reaches a substantially linear increase with a change in opening angle, the second valve begins to open, allowing better flow modulation with equal maximum flow capacity. Without being bound to a particular theory of the operation of the present invention, it is believed that maximum flow capacity and modulation of the flow are optimized by proper selection of the port diameters for total flow area with greatest differential in port area.

In accordance with a first embodiment of the present invention, a turbocharger system is provided, comprising: (1) a high-pressure turbocharger unit; (2) a low-pressure turbocharger unit operably associated with the high-pressure turbocharger unit; and (3) a valve system operably associated with either of the high-pressure and low-pressure turbocharger units, wherein the valve system includes at least two valve members operable to selectively meter a gas flow to either of the high-pressure or low-pressure turbocharger units.

In accordance with a second embodiment of the present invention, a turbocharger system is provided, comprising: (1) a high-pressure turbocharger unit having a turbine portion; (2) a low-pressure turbocharger unit having a turbine portion, wherein the low-pressure turbocharger unit is operably associated with the high-pressure turbocharger unit; and (3) a valve system operably associated with either of the turbine portions of the high-pressure and low-pressure turbocharger units, wherein the valve system includes at least two valve members operable to selectively meter a gas flow to either of the turbine portions of the high-pressure or low-pressure turbocharger units.

In accordance with a third embodiment of the present invention, a turbocharger system is provided, comprising: (1) a high-pressure turbocharger unit having a turbine portion; (2) a low-pressure turbocharger unit having a turbine portion, wherein the low-pressure turbocharger unit is operably associated with the high-pressure turbocharger unit; and (3) a valve system operably associated with either of the turbine portions of the high-pressure and low-pressure turbocharger units, wherein the valve system includes at least two valve members operable to selectively meter a gas flow to either of the turbine portions of the high-pressure or low-pressure turbocharger units, wherein the valve members are operable to be independently or sequentially actuated by the valve system.

In accordance with a fourth embodiment of the present invention, a turbocharger system is provided, comprising: (1) a high-pressure turbocharger unit; (2) a low-pressure turbocharger unit operably associated with the high-pressure turbocharger unit; and (3) a valve system operably associated with either of the high-pressure and low-pressure turbocharger units, wherein the valve system includes at least two valve members operable to selectively meter a gas flow to either of the high-pressure or low-pressure turbocharger units, wherein the valve members are asymmetric with respect to one another.

In accordance with a fifth embodiment of the present invention, a turbocharger system is provided, comprising: (1) a high-pressure turbocharger unit having a turbine portion; (2) a low-pressure turbocharger unit having a turbine portion, wherein the low-pressure turbocharger unit is operably associated with the high-pressure turbocharger unit; and (3) a valve system operably associated with either of the turbine portions of the high-pressure and low-pressure turbocharger units, wherein the valve system includes at least two valve members operable to selectively meter a gas flow to either of the turbine portions of the high-pressure or low-pressure turbocharger units, wherein the valve members are asymmetric with respect to one another.

In accordance with a sixth embodiment of the present invention, a turbocharger system is provided, comprising: (1) a high-pressure turbocharger unit having a turbine portion; (2) a low-pressure turbocharger unit having a turbine portion, wherein the low-pressure turbocharger unit is operably associated with the high-pressure turbocharger unit; and (3) a valve system operably associated with either of the turbine portions of the high-pressure and low-pressure turbocharger units, wherein the valve system includes at least two valve members operable to selectively meter a gas flow to either of the turbine portions of the high-pressure or low-pressure turbocharger units, wherein the valve members are operable to be independently or sequentially actuated by the valve system, wherein the valve members are asymmetric with respect to one another.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. 1A is a perspective view illustrating a regulated two-stage turbocharger system, in accordance with the general teachings of the present invention;

FIG. 1B is a side elevational view of the regulated two-stage turbocharger system depicted in FIG. 1A, in accordance with the general teachings of the present invention;

FIG. 1C is a front elevational view of the regulated two-stage turbocharger system depicted in FIG. 1A, in accordance with the general teachings of the present invention;

FIG. 2 is a front perspective view of an alternative regulated two-stage turbocharger system, in accordance with a first embodiment of the present invention;

FIG. 3 is a rear perspective view of the alternative regulated two-stage turbocharger system depicted in FIG. 2, in accordance with a first embodiment of the present invention; and

FIG. 4 is a schematic view of a second alternative regulated two-stage turbocharger system, in accordance with a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description of the embodiment(s) of the present invention is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

With respect to the use of “fluid,” as that term is used herein, it is meant to include any gaseous material including but not limited to air, exhaust gas, and/or the like.

With respect to the use of “fluid communication,” as that phrase is used herein, it is meant to include any structure that permits one component to receive and/or introduce a fluid to or into a second component including but not limited to pipes, conduits, tubes, hoses, and/or the like, those terms being used interchangeably herein.

With respect to the use of “gas flow,” as that phrase is used herein, it is meant to include any gas flow or stream including but not limited to an air flow, an exhaust gas flow, and/or the like.

Referring to the Figures generally, and specifically to FIGS. 1-3, a regulated two-stage turbocharger assembly is shown generally at 10. The assembly 10 includes two exhaust gas turbine systems 12, 14, respectively. The associated compressor systems are not shown for purposes of clarity.

The first turbine system 12 is a high-pressure turbine, connected in series with the low-pressure turbine system 14. The assembly 10 also includes intake pipe 16, which is connected to a high-pressure turbine pipe 18. A first intake port 20 operates in conjunction with a second intake port 22 to feed exhaust gases from the vehicle's engine (not shown) into either the intake pipe 16, or the port intake pipes 24 of the assembly 10.

During normal turbocharging operation, at low engine speed, the exhaust gases from the engine do not generate enough energy to operate one large, low-pressure turbine, similar to the low-pressure turbine 14, but those same exhaust gases do provide enough energy to operate a smaller turbine, such as the high-pressure turbine 12. In a first mode of operation, the exhaust gases sequentially flow into the first intake port 20, the second intake port 22, the intake pipe 16, the high-pressure turbine pipe 18, and then finally into the high-pressure turbine 12. The high-pressure turbine then spins its associated compressor (element 32 as shown in FIG. 2) thus providing pressurized air to be forced back into the intake manifold so as to increase engine power and torque. As the engine speed increases, so does exhaust gas pressure and energy.

In accordance with one aspect of the present invention, the exhaust flow from the high-pressure turbine 12 enters the low-pressure turbine 14 in series. This is important even when there is not enough energy to drive the low-pressure turbine 14. As the speed and load build, the low-pressure turbine 14, in series with the high-pressure turbine 12, both provide intake pressure increase.

In accordance with one aspect of the present invention, the first port 20 and the second port 22 are in communication with one another through intake pipe 16, which allows for asymmetric valves to operate with independent control in transition from a first mode (e.g., light load) to fully open in a second mode (e.g., heavy load). Accordingly, it is noteworthy that the pressure is balanced between the left and right side exhaust manifolds. Without communication between ports 20, 22, respectively, the engine will not be pressure balanced.

In a second mode of operation, the exhaust gas from the engine passes through the port intake pipes 24 and flows directly into the low-pressure turbine 14, bypassing the high-pressure turbine 12, and spinning its associated compressor (element 34 as shown in FIG. 2), providing compressed air to the intake manifold of the engine at high engine speeds. The high-pressure turbine 12 loses its effectiveness at higher engine speeds, and the larger, low-pressure turbine 14 is used to effectively increase engine power at the higher engine speed range.

The present invention overcomes the problem of poor transition characteristics from the high-pressure turbine to the low-pressure turbine, typically found in conventional regulated two-stage turbocharger systems, and allows for a smooth transition from the high-pressure turbine 12, which affects performance mainly at low engine speeds, to the low-pressure turbine 14, which affects performance mainly at high engine speeds. The present invention employs a valve system 26 that is operable to selectively control the flow of exhaust gas to both the high- and low-pressure turbines 12, 14, respectively.

In accordance with one aspect of the present invention, the valve system 26 is operable to control, either independently or sequentially, at least one valve member, and, in accordance with another aspect of the present invention, at least two valve members so as to control gas flow (e.g., exhaust gas) therethrough. In accordance with still another aspect of the present invention, the valve members of the valve system 26 are asymmetric with respect to one another, such as but not limited to having differing diameters (e.g., port diameters). In accordance with yet another aspect of the present invention, the valve members of the valve system 26 have differing areas (e.g., perimeters, diameters, and/or the like) with respect to one another.

As previously noted, as the engine speed increases, so does exhaust mass flow and pressure. When the exhaust pressure reaches a certain predetermined value, a relatively small valve member 28 (e.g., disposed within or in operable association with the valve system 26) opens to begin to allow exhaust gas to bypass the high-pressure turbine 12 and flow directly into the low-pressure turbine 14. As the exhaust pressure continues to increase, a relatively large valve member 30 (e.g., also disposed within or in operable association with the valve system 26) begins to open, allowing even more high pressure exhaust gas to flow into the low-pressure turbine 14. The opening and closing of the small valve member 28 and the large valve member 30 can be controlled in such a way as to provide a smooth transition from using the high-pressure turbine 12 to the low-pressure turbine 14 and thus eliminate or at least lessen the momentary reduction of torque at the transition between the high pressure turbine and the low pressure turbine operation.

By way of a non-limiting example, the valve members, 28, 30, respectively, can be configured in any number of shapes, including but not limited to circles, ovals, squares, rectangles, and/or the like.

By way of a non-limiting example, the valves members 28, 30, respectively, can be controlled in any number of ways, including mechanically (e.g., springs or other biasable members, lost motion devices, and/or the like), pneumatically, electronically (e.g., through pulse width modulated (PWM) solenoids), or a combination of mechanical, pneumatic, and/or electronic methods. Additionally, additional control mechanisms, such as but not limited to the vehicle's ECU, e.g., in conjunction with appropriate monitoring devices, can monitor and/or control the function of the valve system 26.

In accordance with a first alternative embodiment of the present invention, the intended operation of the flow for both the intake and exhaust gases will now be described with specific reference to FIGS. 2 and 3.

The exhaust gas flows into the first intake port 20 and the second intake port 22. When the valve members 28 and 30 are closed, the gas then flows through high-pressure turbine 12, and into the low-pressure turbine 14. The high-pressure turbine 12 is operably connected to a compressor 32. As the high-pressure turbine 12 increases speed, the compressor 32 also increases speed, and fresh air coming in from a tube portion 36 is compressed and forced out into another tube portion 38. The pressurized air is then transferred into still another tube portion 40, and eventually into the intake manifold of the engine.

When both the small and large valve members 28, 30, respectively, are fully opened, the exhaust gas flows directly into the low-pressure turbine 14. The low-pressure turbine 14 is operably connected with a compressor 34, and increases in rotational speed as the low-pressure turbine 14 increases in speed. The compressor 34 receives air from a large intake pipe 42, compresses it, and then the high-pressure gas flows out of the tube portion 40. The tube portion 40 preferably includes a first connector tube 44 for feeding air through the tube portion 36 and into the compressor 32, and a second connector tube 46 for transferring air after it has been pressurized from the tube portion 38 to the tube portion 40. A tube portion 48 allows the exhaust gas passing through the low-pressure turbine 14 to be fed into the exhaust system of the vehicle.

Referring to FIG. 4, there is shown a schematic view of a second alternative regulated two-stage turbocharger system, in accordance with a second embodiment of the present invention.

A regulated two-stage turbocharger system is generally shown at 100. The turbocharger system 100 includes two exhaust gas turbine systems 102, 104, respectively. The associated compressor systems 106, 108, respectively, are operably associated with turbine systems 102, 104, respectively, e.g., via shaft members 102 a, 104 a, respectively.

The first turbine system 102 is a high-pressure turbine, operably associated with, in fluid communication with, and/or connected in series with the low-pressure turbine system 104. High-pressure turbine system 102 is in fluid communication with an engine system 110, e.g., via an exhaust manifold system 112, e.g., via conduit 114. High-pressure turbine system 102 is in fluid communication with low-pressure turbine system 104, e.g., via conduit 116.

Exhaust manifold system 112 is operably associated and/or in fluid communication with an engine 118, e.g., via conduit 120. In this manner, exhaust gas emanating from the operation of the engine 118, e.g., via exhaust banks 122, 124, respectively, is directed, e.g., via conduits 122 a, 124 a, respectively, through an optional EGR valve 126 to the exhaust manifold system 112, wherein it can be ultimately directed to the turbocharger system 100. Additionally, an intake manifold system 128 is operably associated and/or in fluid communication with engine 118, e.g., via conduit 130, so as to be able to introduce air into engine system 110, specifically cylinders 132, e.g., via conduits 132 a. An optional intercooler system 134 is operably associated and/or in fluid communication with the intake manifold, e.g., via conduit 130. An optional second intercooler system 134 a is operably associated and/or in fluid communication with either of the compressor systems 106, 108, respectively. Although a V-8 engine system is shown, it should be appreciated that the present invention can be practiced with any type of engine configuration, including but not limited to V-4, V-6, and/or inline engine configurations (e.g., 1-4, 1-5, 1-6 and/or the like).

The present invention employs an optional valve system 200 that is operable to selectively control the flow of exhaust gas to the low-pressure turbine system 104, thus being operable to better match gas flow conditions/requirements and improve the overall response and performance of the turbocharger system 100.

In accordance with one aspect of the present invention, the valve system 200 is selectively operable to control, either independently or sequentially, at least two turbine regulating valve members 202, 204, respectively, so as to control gas flow (e.g., exhaust gas flow) therethrough, e.g., through low-pressure turbine system 104.

In accordance with one aspect of the present invention, the valve system 200 is operable to control, either independently or sequentially, at least one valve member, and, in accordance with another aspect of the present invention, at least two valve members so as to control gas flow (e.g., exhaust gas) therethrough. In accordance with still another aspect of the present invention, the valve members of the valve system 200 are asymmetric with respect to one another, such as but not limited to having differing diameters (e.g., port diameters). In accordance with yet another aspect of the present invention, the valve members of the valve system 200 have differing areas (e.g., perimeters, diameters, and/or the like) with respect to one another.

The turbine regulating valve members 202, 204, respectively, are in fluid communication with the exhaust manifold system 112, e.g., via conduits 202 a, 204 a, respectively. The turbine regulating valve members 202, 204, respectively, are also in fluid communication with the low-pressure turbine portion 104, e.g., via conduit 206. A conduit 208 allows exhaust gas to pass out of the low-pressure turbine portion 104, e.g., to a waste gate or to an exhaust system (not shown). An optional waste gate or turbine by-pass system (e.g., a valve member) 300 is in fluid communication with conduits 300 a and 300 b, the intended purpose of which will be described herein.

By way of a non-limiting example, the turbine regulating valves members 202, 204, respectively, can be controlled in any number of ways, including mechanically (e.g., springs or other biasable members, lost motion devices, and/or the like), pneumatically, electronically (e.g., through pulse width modulated (PWM) solenoids), or a combination of mechanical, pneumatic, and/or electronic methods. Additionally, additional control mechanisms, such as but not limited to the vehicle's ECU, e.g., in conjunction with appropriate monitoring devices, can monitor and/or control the function of the valve system 200, and more specifically, the turbine regulating valve members 202, 204, respectively.

By way of a non-limiting example, the optional waste gate or turbine by-pass valve member 300 can be controlled in any number of ways, including mechanically (e.g., springs or other biasable members, lost motion devices, and/or the like), pneumatically, electronically (e.g., through pulse width modulated (PWM) solenoids), or a combination of mechanical, pneumatic, and/or electronic methods. Additionally, additional control mechanisms, such as but not limited to the vehicle's ECU, e.g., in conjunction with appropriate monitoring devices, can monitor and/or control the function of the waste gate or turbine by-pass valve member 300.

An optional compressor by-pass system (e.g., a valve member) 400 is in fluid communication with the high-pressure compressor portion 106, the intended purpose of which will be described herein. In accordance with one aspect of the present invention, the compressor by-pass system 400 is passively-controlled. The compressor by-pass valve member 400 is also in fluid communication with conduit 400 a (which exits from low-pressure compressor portion 108) and conduit 400 b (which enters the optional intercooler system 44), e.g., via conduits 400 c and 400 d. The intended purpose of the compressor by-pass valve member 400 will be described herein. Fresh air is introduced into low-pressure compressor system 108, and components downstream thereof, via conduit 108 a.

Where low engine speed and load conditions are present, the engine speed and load are relatively low, the resulting exhaust mass flow and pressure are also relatively low. In this case, the engine 118 is running and producing an exhaust gas flow, which is eventually directed through the exhaust manifold system 112. The turbine regulating valves 202, 204, respectively, the optional waste gate or turbine by-pass valve member 300, and the optional compressor by-pass valve member 400 are all closed, i.e., an exhaust gas flow cannot proceed therethrough. As previously noted, the active control of one or more of these various valve members can be achieved through the use of the vehicle's ECU, as well as various sensors in communication therewith.

As such, the exhaust gas flow has to flow through the high-pressure turbine system 102. As the high-pressure turbine system 102 is in fluid communication with the low-pressure turbine system 104, e.g., via conduit 116, at least a portion of the exhaust gas flow is introduced into the low-pressure turbine system 104.

As the high-pressure turbine system 102 increases speed, the associated high-pressure compressor system 106 also increases speed. The low-pressure turbine system 104 also increases speed to a certain extent, albeit to a lesser extent than the high-pressure turbine system 102, and the associated low-pressure compressor system 108 also increases speed to a certain extent, albeit to a lesser extent than the high-pressure compressor system 106. In this manner, fresh air, e.g., coming in from conduit 108 a, is compressed, e.g., via low-pressure compressor system 108 and high-pressure compressor system 106, and eventually introduced into the intake manifold 128 of the engine 118.

Where transitional engine speed and load conditions are present, the engine speed and load are increasing, the resulting exhaust mass flow and pressure are also increasing. In this case, the engine 118 is still running and producing an increasing exhaust gas flow, which again is eventually directed through the exhaust manifold system 112. The turbine regulating valve 204, the waste gate or turbine by-pass valve member 300, and the compressor by-pass valve member 400 are all closed, i.e., an exhaust gas flow cannot proceed therethrough. As previously noted, the active control of one or more of these various valve members can be achieved through the use of the vehicle's ECU, as well as various sensors in communication therewith. However, turbine regulating valve 202 is open, i.e., an exhaust gas flow can proceed therethrough.

As such, at least a portion of the exhaust gas flow has to flow through the high-pressure turbine system 102. As the turbine regulating valve 202 is in fluid communication with the low-pressure turbine system 104, e.g., via conduit 206, at least a portion of the exhaust gas flow is introduced into the low-pressure turbine system 104.

As the high-pressure turbine system 102 increases speed, the associated high-pressure compressor system 106 also increases speed. The low-pressure turbine system 104 also increases speed to that of around the high-pressure turbine system 102, and the associated low-pressure compressor system 108 also increases speed to an extent of about the high-pressure compressor system 106. In this manner, fresh air, e.g., coming in from conduit 108 a, is compressed, e.g., via low-pressure compressor system 108 and high-pressure compressor system 106, and eventually introduced into the intake manifold 128 of the engine 118.

Where rated engine speed and load conditions are present, the engine speed and load have reached their maximum levels, the resulting exhaust mass flow and pressure have also reached their maximum levels. In this case, the engine 118 is again still running and producing a maximum exhaust gas flow, which again is eventually directed through the exhaust manifold system 112. The turbine regulating valves 202, 204, respectively, optionally, the waste gate or turbine by-pass valve member 300, and, optionally, the compressor by-pass valve member 400 are all open, i.e., an exhaust gas flow can proceed therethrough. As previously noted, the active control of one or more of these various valve members can be achieved through the use of the vehicle's ECU, as well as various sensors in communication therewith.

As such, the exhaust gas flow, or at least a major portion thereof, does not flow through the high-pressure turbine system 102, i.e., the high-pressure turbine system 102 is essentially by-passed. As the exhaust manifold system 112 is in fluid communication with the turbine by-pass system 200, e.g., via conduits 202 a, 204 a, respectively, all, or at least a major portion of the exhaust gas flow is introduced into the low-pressure turbine system 104. Because waste gate or turbine by-pass valve member 300 is also open, at least a portion of the exhaust gas flow can by-pass the low-pressure turbine system 104, e.g., if the exhaust gas flow pressure exceeds a predetermined level that could potentially damage the low-pressure turbine system 104, or any other components of the turbocharger system 100 and/or engine system 110.

As the low-pressure turbine system 104 is at maximum speed, the associated high-pressure compressor system 108 also reaches maximum speed. In this manner, fresh air, e.g., coming in from conduit 108 a, is compressed, e.g., via low-pressure compressor system 108, and eventually introduced into the intake manifold 128 of the engine 118. Although the high-pressure turbine system 102 is essentially by-passed, a minimal amount of exhaust gas flow may pass therethrough, which can cause the associated high-pressure compressor system 106 to be actuated to a certain extent. Even if this occurs, the compressor by-pass valve member 400 is open, so that the high-pressure compressor system 106 is by-passed or essentially by-passed. The intended purpose of the compressor by-pass valve member 400 is to prevent damage to the high-pressure compressor system 106 when the high velocity air flow coming from the low-pressure compressor system 108 exits therefrom, e.g., via conduit 400 a. Additionally, the compressor by-pass valve member 400 also improves overall system efficiency. Thus, the high velocity air flow can instead travel through conduits 400 c, 400 d, respectively, into conduit 400 b and eventually into the intake manifold 122.

The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention. 

1. A turbocharger system, comprising: a high-pressure turbocharger unit; a low-pressure turbocharger unit operably associated with the high-pressure turbocharger unit; and a valve system operably associated with either of the high-pressure and low-pressure turbocharger units; wherein the valve system includes at least two valve members operable to selectively meter a gas flow to either of the high-pressure or low-pressure turbocharger units.
 2. The invention according to claim 1, wherein the high-pressure turbocharger unit includes a turbine portion and a compressor portion, wherein the turbine portion and the compressor portion of the high-pressure turbocharger unit are operably associated therebetween.
 3. The invention according to claim 2, wherein the low-pressure turbocharger unit includes a turbine portion and a compressor portion, wherein the turbine portion and the compressor portion of the low-pressure turbocharger system are operably associated therebetween, wherein the compressor portion of the high-pressure turbocharger unit is in fluid communication with the compressor portion of the low-pressure turbocharger unit.
 4. The invention according to claim 3, further comprising a compressor by-pass system operably associated with the high-pressure compressor unit, wherein the compressor by-pass system is selectively operable to cause at least a portion of an air flow to by-pass the high-pressure compressor portion.
 5. The invention according to claim 1, wherein the valve system includes at least two valve members selectively operable to meter an exhaust gas flow to the low-pressure turbine portion.
 6. The invention according to claim 5, wherein the at least two valve members are operable to independently meter an exhaust flow to the low-pressure turbine portion.
 7. The invention according to claim 5, wherein the at least two valve members are operable to sequentially meter an exhaust flow to the low-pressure turbine portion.
 8. The invention according to claim 1, further comprising a turbine by-pass system operably associated with the low-pressure turbine portion, wherein the turbine by-pass system is selectively operable to cause at least a portion of the exhaust gas flow to by-pass the low-pressure turbine portion.
 9. The invention according to claim 8, wherein at least one of the two valve members is in fluid communication with the turbine by-pass system.
 10. A turbocharger system, comprising: a high-pressure turbocharger unit having a turbine portion; a low-pressure turbocharger unit having a turbine portion, wherein the low-pressure turbocharger unit is operably associated with the high-pressure turbocharger unit; and a valve system operably associated with either of the turbine portions of the high-pressure and low-pressure turbocharger units; wherein the valve system includes at least two valve members operable to selectively meter a gas flow to either of the turbine portions of the high-pressure or low-pressure turbocharger units.
 11. The invention according to claim 10, wherein the high-pressure turbocharger unit includes a compressor portion, wherein the turbine portion and the compressor portion of the high-pressure turbocharger unit are operably associated therebetween.
 12. The invention according to claim 11, wherein the low-pressure turbocharger unit includes a compressor portion, wherein the turbine portion and the compressor portion of the low-pressure turbocharger system are operably associated therebetween, wherein the compressor portion of the high-pressure turbocharger unit is in fluid communication with the compressor portion of the low-pressure turbocharger unit.
 13. The invention according to claim 12, further comprising a compressor by-pass system operably associated with the high-pressure compressor unit, wherein the compressor by-pass system is selectively operable to cause at least a portion of an air flow to by-pass the high-pressure compressor portion.
 14. The invention according to claim 10, wherein the valve system includes at least two valve members selectively operable to meter an exhaust gas flow to the low-pressure turbine portion.
 15. The invention according to claim 14, wherein the at least two valve members are operable to independently meter an exhaust flow to the low-pressure turbine portion.
 16. The invention according to claim 14, wherein the at least two valve members are operable to sequentially meter an exhaust flow to the low-pressure turbine portion.
 17. The invention according to claim 10, further comprising a turbine by-pass system operably associated with the low-pressure turbine portion, wherein the turbine by-pass system is selectively operable to cause at least a portion of the exhaust gas flow to by-pass the low-pressure turbine portion.
 18. The invention according to claim 17, wherein at least one of the two valve members is in fluid communication with the turbine by-pass system.
 19. A turbocharger system, comprising: a high-pressure turbocharger unit having a turbine portion; a low-pressure turbocharger unit having a turbine portion, wherein the low-pressure turbocharger unit is operably associated with the high-pressure turbocharger unit; and a valve system operably associated with either of the turbine portions of the high-pressure and low-pressure turbocharger units; wherein the valve system includes at least two valve members operable to selectively meter a gas flow to either of the turbine portions of the high-pressure or low-pressure turbocharger units; wherein the valve members are operable to be independently or sequentially actuated by the valve system.
 20. The invention according to claim 19, wherein the valve system includes at least two valve members selectively operable to meter an exhaust gas flow to the low-pressure turbine portion. 